.\" $OpenBSD: EVP_PKEY_cmp.3,v 1.14 2024/03/05 19:21:31 tb Exp $
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.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
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.Dd $Mdocdate: March 5 2024 $
.Dt EVP_PKEY_CMP 3
.Os
.Sh NAME
.Nm EVP_PKEY_missing_parameters ,
.Nm EVP_PKEY_copy_parameters ,
.Nm EVP_PKEY_cmp_parameters ,
.Nm EVP_PKEY_cmp
.\" .Nm EVP_PKEY_save_parameters is intentionally undocumented
.\" because nothing uses it according to codesearch.debian.net
.\" and it only affects X509_PUBKEY_set(3) for DSA,
.\" resulting in incomplete output without the public key parameters.
.Nd public key parameter and comparison functions
.Sh SYNOPSIS
.In openssl/evp.h
.Ft int
.Fo EVP_PKEY_missing_parameters
.Fa "const EVP_PKEY *pkey"
.Fc
.Ft int
.Fo EVP_PKEY_copy_parameters
.Fa "EVP_PKEY *destination"
.Fa "const EVP_PKEY *source"
.Fc
.Ft int
.Fo EVP_PKEY_cmp_parameters
.Fa "const EVP_PKEY *a"
.Fa "const EVP_PKEY *b"
.Fc
.Ft int
.Fo EVP_PKEY_cmp
.Fa "const EVP_PKEY *a"
.Fa "const EVP_PKEY *b"
.Fc
.Sh DESCRIPTION
.Fn EVP_PKEY_missing_parameters
checks whether any public key parameters are missing from
.Fa pkey .
.Pp
.Fn EVP_PKEY_copy_parameters
copies all public key parameters from the
.Fa source
to the
.Fa destination .
If the algorithm does not use parameters, no action occurs.
.Pp
.Fn EVP_PKEY_cmp_parameters
compares the public key parameters of
.Fa a
and
.Fa b .
This is only supported for algorithms that use parameters.
.Pp
.Fn EVP_PKEY_cmp
compares the public key components of
.Fa a
and
.Fa b .
If the algorithm uses public key parameters,
it also compares the parameters.
.Pp
The main purpose of the functions
.Fn EVP_PKEY_missing_parameters
and
.Fn EVP_PKEY_copy_parameters
is to handle public keys in certificates where the parameters are
sometimes omitted from a public key if they are inherited from the CA
that signed it.
.Pp
Since OpenSSL private keys contain public key components too, the
function
.Fn EVP_PKEY_cmp
can also be used to determine if a private key matches a public key.
.Sh RETURN VALUES
.Fn EVP_PKEY_missing_parameters
returns 1 if the public key parameters of
.Fa pkey
are missing or incomplete or 0 if they are present and complete
or if the algorithm doesn't use parameters.
.Pp
.Fn EVP_PKEY_copy_parameters
returns 1 for success or 0 for failure.
In particular, it fails if the key types mismatch or if the public
key parameters in the
.Fa source
are missing or incomplete.
.Pp
.Fn EVP_PKEY_cmp_parameters
and
.Fn EVP_PKEY_cmp
return 1 if the keys match, 0 if they don't match, -1 if the key types
are different and -2 if the operation is not supported.
.Sh SEE ALSO
.Xr EVP_PKEY_asn1_set_public 3 ,
.Xr EVP_PKEY_CTX_new 3 ,
.Xr EVP_PKEY_keygen 3 ,
.Xr EVP_PKEY_new 3 ,
.Xr X509_get_pubkey_parameters 3
.Sh HISTORY
.Fn EVP_PKEY_missing_parameters
and
.Fn EVP_PKEY_copy_parameters
first appeared in SSLeay 0.8.0.
.Fn EVP_PKEY_cmp_parameters
first appeared in SSLeay 0.9.0.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn EVP_PKEY_cmp
first appeared in OpenSSL 0.9.8 and has been available since
.Ox 4.5 .
